public class Test {
    public static void main(String[] args) {
        int a = 90;
        boolean flag = true;
        for(int i =2; i <= Math.sqrt(a); i++){
            if(a % i == 0){
                System.out.println("不是质数");
                flag = false;
                break;
            }
        }
        if(flag){
            System.out.println("是质数");
        }
    }
}
